Add TimescaleDB extension support

[shusaan]

This PR adds support for the timescaledb extension to the postgres-extensions-containers project.

This PR supersedes #30 and incorporates the same changes, addressing the feedback and discussion from that PR.

Closes #58

Changes

• Added timescaledb directory with Dockerfile and metadata.hcl
• Updated CI/CD workflows to include timescaledb in the build pipeline

[gbartolini]

Hi @shusaan, can you please resubmit the PR by following the scaffolding instructions and then the local testing part in the BUILD.md file? Thanks.

[gbartolini]

Hi @shusaan, can you please update your PR using the new scaffolding procedure and making sure you test it? Also, please use the official PGDG packages, as they are available there (we prefer the Postgres official source).

Finally, can you please write some smoke tests that verify that Timescale is installed? (look at the PostGIS extension for examples).

[shusaan]

Hi @gbartolini,

I've investigated using PGDG packages for TimescaleDB as requested.

The issue: The PGDG package postgresql-18-timescaledb contains both Apache 2.0 and TSL (Timescale License) code. There is no Apache 2.0-only package available in the official PGDG repository.

I verified this by running:

apt-cache policy postgresql-18-timescaledb    # Available in PGDG
apt-cache policy timescaledb-2-oss-postgresql-18  # Not found

The Apache 2.0-only packages (timescaledb-2-oss-postgresql-*) are only available from TimescaleDB's own repository (packagecloud.io), not from PGDG.

Options:

Keep using TimescaleDB's repository with the OSS package (current approach). Here is discussion about TimescaleDB License.

What do you suggest?